Here is an original MC Gregory "Master" 518M. This piece measures .068" on my gauge.
These were produced in various iterations after the Model A was discontinued. This appears to be a later one with the squared off shank. While the geometry remained the same, there seems to be less hand work on this generation, featuring slightly thicker rails and a sandblasted chamber. I believe these are the inspiration for the Vandoren small chamber design.
This piece is good as is or can be opened to produce a very modern sounding setup with great stability and focus.